Seismo-Microplasticity phenomenon in the rocks

Abstract

The seismic records of borehole-to-borehole me- asurements on frequency of 200 Hz in the mi-crostrain range have been analysed. Microplas-ticity manifestations caused by seismic wave are detected on seismic records. It is the lad-der-like stepwise change in amplitude course in some parts of the seismic trace. The step dura-tion (time plateau) presents the amplitude- dependent time delay that shifts the arrival time and protracts pulse front. The microplastic process occurs owing to the anomalous re-alignment of the internal stresses on the micro-structural defects in “elastic” domain. Result is the useful contribution for improvement of the theory of wave attenuation in the rocks. It can also be used in solving the applied problems in material science, seismic prospecting, diagnos-tics etc

Microplasticity effect in low-velocity zone induced by seismic wave

“…There are also attempts of theoretical justification of the wave attenuation mechanism in the rocks with microplasticity manifestations (Yarushina and Podladchikov, 2008;2010). The wave attenuation mechanism in Earth materials is more complicated than in other solid states, therefore the combination of known mechanisms is possible, for instance, as the hybrid relaxation-hysteresis mechanism (Mashinskii, 2006).…”

“…The flat steps on the seismic trace are interpreted as the short-duration interruption in the stress course (Mashinskii, 2010;Sapozhnikov et al, 1996). In the stress-strain curve, such stops take place owing to the microplasticity when the stress reaches some critical value σ cr .…”

“…The signs of microplasticity take place on many seismic records. Seismic microplasticity manifestations (SMM) take place in signals both with low and high intensity or small and great deformation rate (Mashinskii, 2010). Signal intensity coupled with deformation rate determines the amplitude steepness R A/t .…”

“…Dynamic microplasticity in geologic materials is not yet studied. However this study is going on in the experimental and theoretical plan (Braccini et al, 2000;Mashinskii, 2008;2010;Xu et al, 1998;Yarushina and Podladchikov, 2008;2010).…”

“…The first estimate of microplasticity manifestation on seismic records was made in the work (Mashinskii, 2010). During pulse propagation with diverse amplitudes, shift of the arrival time and the pulse front protracting has been detected.…”